Japanese Sword Wiping, Oil Removal, and Appreciation Protocol: The Professional Care Sequence Practiced by Swordsmiths and Polishers

The Essence of Maintenance: Japanese Swords Are "Living" Metal

Before discussing Japanese sword maintenance, it's essential to understand that these blades are "living" objects. As composite materials of repeatedly folded and hammered steels with varying carbon content, their metallurgical structure constantly responds to Japan's hot and humid climate. Neglect allows rust to penetrate from the surface into the blade's internal structure, causing irreversible damage.

However, "performing maintenance" and "performing correct maintenance" are entirely different matters. Improper care—excessive abrasion, wiping with rough cloth, using inappropriate oils—causes more serious damage than rust itself. This article explains the precise procedures actually employed by swordsmiths and polishers.

The Basic Kit: Tool Selection and Preparation

Professional maintenance requires the following tools:

Essential Tools

• Nuguigami (wiping paper): Soft hosho Japanese washi paper. Tissue and cotton cloth are unsuitable as their fibers can scratch the blade.
• Uchiko powder: Ground whetstone powder wrapped in gauze, serving as a mild abrasive that absorbs and removes old oil and grime.
• Choji oil: Traditional anti-rust oil derived from clove. It resists spoilage and forms a stable protective film on sword steel. Use commercially available "sword-grade choji oil."
• Mekugi-nuki: Brass pin used to remove the mekugi (retaining pin) when detaching the tsuka from the blade.
• Gloves: Thin nitrile rubber gloves preventing fingerprint oils from contacting the blade.

Standard Maintenance Procedure (Monthly to Bi-Monthly)

Step 1: Remove the Tsuka (When Necessary)

For inspection or thorough maintenance, first use the mekugi-nuki to remove the mekugi and detach the tsuka. The recommended method is to hold the blade near the nakago with one hand while lightly tapping the kashira (pommel) with the heel of the other hand—not to tap the tsuka downward with the blade pointing down, which risks sudden blade exposure.

Step 2: Remove Old Oil (Nuguai/Wiping)

Use nuguigami to wipe away old oil across the entire blade. Always wipe in one direction only: from the mune (back of the blade) toward the edge. Bidirectional wiping scratches the blade surface. This initial wipe requires light pressure—the goal is absorption, not scrubbing.

Step 3: Apply Uchiko Powder

After removing the bulk of the oil, lightly tap uchiko powder onto the hira-ji (flat surface) and mune side of the blade, then wipe it away in the same direction (mune to edge) with clean nuguigami. Since uchiko contains abrasive stone powder, excessive use micro-abrades the blade surface. For routine monthly maintenance, one to two applications are sufficient.

Step 4: Apply Fresh Oil

Place a few drops of choji oil on the edge of a clean piece of nuguigami and spread it thinly and evenly across the entire blade surface. The correct amount creates just a slight sheen—excess oil seeps into the saya's wooden interior, causing deterioration. Apply to all surfaces: hira-ji, shinogi-ji (area above the ridge), edge, and mune.

Step 5: Replace the Tsuka and Store

Once oil is evenly applied, return the blade to its tsuka in the correct orientation and reinsert the mekugi. Store with the edge facing up (haki-age), with the saya horizontal or slightly tilted toward the edge side.

Oil Removal (Nuguai): Professional Pre-Polish Preparation

"Oil removal" (abura-nuki) is the professional preparation performed by polishers (togishi) before grinding—fundamentally different from routine maintenance.

Swords submitted for polishing typically carry thick accumulated oil films. Applying whetstones to such surfaces clogs the stone's grinding surface, reducing efficiency and creating uneven results. Oil removal eliminates this film completely.

The Oil Removal Process

Polishers achieve complete oil removal either by multiple careful wipes with generous uchiko applications, or by applying ethanol-based solvents that fully dissolve surface oils. When using solvents, apply uniformly across the entire blade surface and wipe away after several minutes.

After oil removal, the blade surface becomes highly susceptible to rust—polishing work should begin the same day. Collectors performing their own thorough cleaning (not for polishing purposes) must remember to apply a thin coat of choji oil immediately after any complete oil removal.

Appreciation Protocol: How to Properly "See" a Japanese Sword

Equally important to maintenance is the formal appreciation protocol. Correct handling protects the sword while revealing its inherent beauty.

Basic Holding Technique

The formal way to hold a sword for appreciation is edge-up (haki-age), supported with both hands. The right hand lightly grips the tsuka while the left hand supports from below near the shinogi. The cutting edge must never be touched with bare fingers—fingerprint oils immediately initiate oxidation.

Light Angle Technique

Observing jigane texture and hamon accurately requires careful light management. Tilt the blade gently toward a window or fluorescent light source, slowly changing the angle to observe reflections. To see the hamon clearly, angle the edge toward the light source and tilt the blade longitudinally—the nie and niku particle textures become visible. Practitioners call this observation technique "osaete miru" (pressing to see).

Jigane Observation

The grain pattern of the jigane (itame, mokume, masame, etc.) becomes visible by holding the blade horizontal and illuminating it from directly to the side—a different angle than used for hamon observation. Toggle between these two lighting approaches during appreciation.

Observation Sequence

Connoisseurs typically observe in this order: overall shape (sugata) → jigane → hamon → nakago and mei (signature). First assess the overall balance of curvature, length, moto-haba (base width), and saki-haba (tip width) to estimate era and school. Then confirm with detailed jigane and hamon observation. Finally examine the nakago shape, mei, and nengo (era name) inscription.

Storage Environment: Conditions That Make Maintenance Count

Even meticulous maintenance means nothing without proper storage. Optimal conditions for Japanese swords are 15–25°C temperature and 50–60% relative humidity. High humidity promotes steel oxidation; low humidity dries and cracks the wooden saya.

Store in a sword bag (to-fukuro) or paulownia wood box with silica gel desiccant. Sword bags typically use navy or white fukusa-grade silk. When displayed on a katana-kake (sword stand) horizontally, periodically rotate the sword's orientation to prevent oil from pooling in one direction.

Summary: Maintenance Is the Practice of Knowledge and Respect

Japanese sword maintenance is not merely "rust prevention"—it is the practiced knowledge and technique that sustains the blade's life. An ideal cycle consists of monthly to bi-monthly wipe-powder-oil routines, thorough cleaning every six months to a year, and periodic consultation with a professional polisher. With correct knowledge, masterwork blades can be transmitted to future generations in complete condition, even a century hence.